Specialized stretchers are used with emergency vehicles such as ambulances, in part to permit the stretcher to be easily loaded into different ambulances having different internal floor heights. Examples of such prior stretchers are disclosed in U.S. Pat. Nos. 4,097,941, 4,767,148, 4,037,871 and 3,644,944. Although these pre-existing stretchers have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
For example, it is sometimes possible to disengage the releasable locking mechanism when the patient litter is not fully supported by manual lifting, resulting in a rapid drop of the patient litter with an abrupt stop in its lowermost position, which can result in patient injury. Also, prior stretchers may have a pivotally-supported upper body support section which can be maintained in a desired position by a selectively actuatable gas cylinder, but the vertical thickness of the patient litter must usually be increased beyond a desirable amount in order to provide clearance for movement of the gas cylinder with respect to transversely-extending cross members that rigidify the frame.
Accordingly, one object of the present invention is to provide an emergency stretcher with an improved X-frame support, with a safety mechanism which prevents a release of the locking mechanism for the vertical height adjustment except when the patient litter is substantially completely supported by manual or other external lifting forces, and with an arrangement which permits use of a gas cylinder for the upper body support member while maintaining a reasonably compact construction of limited vertical thickness for the patient litter.